Pseudoboiling and heat transfer in a turbulent flow

Kafengauz, N. L.; Fedorov, M. I.

doi:10.1007/bf00828077

Cited by 19 publications

(8 citation statements)

References 3 publications

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“…The existence of liquid-like and gas-like states at supercritical pressures suggests the question as to whether a supercritical state transition akin to subcritical vaporization exists. Similarities have been observed in heat transfer, where oscillations that can be attributed to boiling at subcritical pressure are also observed at moderate supercritical pressure [16,17] -so-called 'pseudoboiling'. Pseudoboiling is associated with the maxima in specific heat capacity and thermal expansion upon crossing the WL, causing a delayed temperature increase and strong expansion when heat is added, similarly to subcritical boiling [18].…”

Section: Introductionsupporting

confidence: 65%

The Latent Heat of Supercritical Fluids

Banuti

2019

Period. Polytech. Chem. Eng.

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The article discusses the notion of a supercritical latent heat during 'pseudoboiling': Experimental, numerical, and theoretical evidence show that the supercritical state space is not homogeneous, but can be divided into liquid-like and gas-like domains, separated by an extension to the coexistence line --the Widom line. The key concept are two limit states of ideal liquid and ideal gas, characterized by constant heat capacities, and analyze the transition between them. Then, analogous to subcritical vaporization, a supercritical state transition from liquid to gaseous overcomes intermolecular attractive forces, albeit over a finite temperature interval rather than at an equilibrium temperature. This distributed latent heat is in fact approximately invariant with respect to pressure for 0 3 < < ( ) p p cr and is thus valid at subcritical and supercritical conditions. This view also changes the perspective on subcritical latent heat: while it is an accurate representation of the required energy at very low pressures, the contribution of the distributed latent heat dominates the equilibrium latent heat as the critical pressure is approached.

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Section: Introductionsupporting

confidence: 65%

The Latent Heat of Supercritical Fluids

Banuti

2019

Period. Polytech. Chem. Eng.

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“…The author proposed a model with liquid-like clusters of molecules below the pseudocritical temperature, and gas-like aggregates above the pseudocritical temperature. Later, Kafangauz [31] argued that this interesting pseudo-boiling was a characteristic of heat transfer under the conditions of P > P cr and T b < T cr < T w . Shitsman [32] also observed the unusual mode of heat transfer, and attributed it to a crisis-like process analogous to the process by which film boiling occurs at subcritical pressures.…”

Section: Introductionmentioning

confidence: 98%

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

Lei

Zhang

et al. 2017

Applied Sciences

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Featured Application: Supercritical carbon dioxide Brayton cycle, geothermal system, nuclear reactor.Abstract: Significant differences in the heat transfer behaviors of supercritical carbon dioxide in a heated channel have been observed at different mass fluxes. At low mass fluxes, a unique heat transfer characteristic is accompanied by a monotonously smooth temperature variation without any temperature peak, even though the ratio of heat flux to mass flux (q/G) is high. In this study, experimental and numerical investigations explore the hidden mechanism of the peculiar heat transfer characteristics of supercritical carbon dioxide at low mass fluxes in vertically upward tubes with inside diameters (ID) of 5 mm. The range of operating conditions examined within the study include a mass flux (G) between 0-200 kg/m 2 s, and a heat flux (q) of up to 120 kW/m 2 . The parametric effects within these experimental conditions were analyzed on the basis of the obtained heat transfer data. Furthermore, a qualitative modeling force analysis and quantitative numerical simulation of vertical flow at low mass flux reveal the heat transfer mechanism for these temperature profiles. In addition, the distribution of flow parameters and thermo-physical properties (such as shear stress, density, and specific heat) in the near-wall region were also studied. It is found that the heat transfer behavior of supercritical CO 2 at low mass flux is similar to "film boiling" at subcritical pressure, where "vapor-like" fluid occupies the sublayer region. Due to reduced buoyancy, the fluid does not cause enough mixing/instability to bring it to the bulk flow.

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“…They observed that the heat transfer would deteriorate and sound oscillation would be produced when the temperature of the working fluid is lower than the pseudo-critical temperature and the pipe wall temperature is higher than this temperature. Kafengauz and Fedorov [9] observed that the heat transfer of pseudo-boiling is accompanied by pressure oscillations. Linne et al [10] conducted a heat transfer experiment on JP-7 and observed that flow oscillations occurred in all the experiments at supercritical pressure.…”

Section: Introductionmentioning

confidence: 99%

Study on influence of forced vibration of cooling channel on flow and heat transfer of hydrocarbon fuel at supercritical pressure

Chen

Han

et al. 2022

Therm sci

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The cooling channel of a scramjet is the fundamental structure of the active thermal protection for an engine. Till now, studies have focused mainly on the steady-state flow and heat transfer process in the cooling channel. However, the vibration intensity of an engine increases sharply as the flight speed increases, because of which, the flow and heat exchange mechanisms based on the cooling channel under stable conditions cannot be applied under vibration. In this study, experimental methods are used to study the characteristics of the forced vibration of a cooling channel on the flow and heat transfer of hydrocarbon fuel at supercritical pressure. In addition, the influences of different vibration frequencies and vibration amplitudes on the flow and heat transfer are analyzed. The research results show that at supercritical pressure, when the fuel temperature is below the critical temperature and the inner wall temperature is above the critical temperature, external vibrations would enhance the heat transfer characteristics of the cooling channel. However, when the pressure and temperature are unstable, the forced vibration of the cooling channel would suppress the instability of temperature and pressure while strengthening the heat exchange.

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Pseudoboiling and heat transfer in a turbulent flow

Cited by 19 publications

References 3 publications

The Latent Heat of Supercritical Fluids

The Latent Heat of Supercritical Fluids

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

Study on influence of forced vibration of cooling channel on flow and heat transfer of hydrocarbon fuel at supercritical pressure

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